Method for regulating the speed of a drive motor

ABSTRACT

The invention involves a process for controlling the rotational speed of a drive motor during a start-up period, in a drive train, containing at least one starter element that can be coupled to the drive motor, in a rotationally fixed manner, in the form of a hydrodynamic coupling, containing a primary blade wheel and a secondary blade wheel, which form together at least one toroid-shaped working space. According to the invention, the rotational speed of the drive motor is set as a function of the power that can be consumed by the hydrodynamic coupling. The consumable power can be controlled or regulated.

[0001] The invention involves a process for controlling the rotationalspeed of a drive motor, in particular, with the characteristics from thegeneric concept of claim 1; furthermore, a use of the process.

[0002] Processes for controlling the rotational speed of a drive motor,in particular, during the start-up period, in a drive train, inparticular for use in motor vehicles, including at least one drive motorand a starter element that can be coupled with it, at least indirectly,are known in a multitude of different embodiments with regard to thevariables triggering the controlling operation, i.e. the input variablesof the control device, the dependence of the control variables on othervariables and the correcting variables. It is generally known that, indrive trains of motor vehicles, including an internal combustion engine,especially Otto or diesel engines, and a starter element that can bemechanically or hydrodynamically coupled to them, as a correctingvariable for the rotational speed control of the drive motor, a variableis formed that at least indirectly characterizes the adjustment of thepower output stage of the drive motor—throttle valve or injectionnozzle—and the adjustment device throttle valve or injection nozzle—istriggered in this way. Reference is made to, as a representativeexample, “Diesel injection technology” by Bosch, VDI-Publishers 1993,pages 162-on. Start-up period is understood here to be the time span ofthe operating period of the drive train, which is characterized by arun-up of the drive unit from the start, i.e. the start-up of the drivemotor until the change into a higher gear level in bypassing thehydrodynamic starter element.

[0003] When hydrodynamic couplings are used as a starter element inmotor vehicles, they are designed in such a manner that a filling canoccur automatically during the start-up period, for example, dependingon the rotational speed of the drive motor or retarded from it. However,it has been shown that dynamic systems behavior becoming set in thisway, characterized by the characteristic line of the coupling, ischaracterized in that high moments can only be transferred at highrotational speeds of the drive motor. This means, however, forembodiment of the drive motor as an internal combustion engine, that theconsumption-optimized range in the performance characteristics of themotor, and thus an operating method that is low in hazardous materials,is not achieved and furthermore, for the transfer of high moments, theprovision of a correspondingly high power by the drive motor is alwaysnecessary.

[0004] The purpose of the invention is thus to develop a process forcontrolling the rotational speed of a drive motor in such a way that thedisadvantages mentioned are prevented and if necessary, theconsumption-optimized ranges, especially in the use of drive motors inthe form of internal combustion engines, optimal from the standpoint ofthe energy content, can be reached in the performance characteristics ofthe drive motor during the start-up period. The solution according tothe invention should be characterized by a low control-technical andregulation-technical expense, as well as a low construction expense.

[0005] The solution according to the invention is characterized by thecharacteristics of claim 1. Advantageous embodiments are given in thedependent claims. Advantageous application possibilities are describedin claims 12 to 15. The control and/or regulation device is described inclaim 16.

[0006] A process for the rotational speed control of a drive motor in adrive train, containing at least one starter element that can beconnected to the drive motor in a rotationally fixed manner in the formof a hydrodynamic coupling, is characterized according to the inventionin that the rotational speed of the drive motor is adjusted depending onthe power that can be consumed by the hydrodynamic coupling as afunction of the rotational speed and torque. This means that upon theappearance of a regulation deviation between a variable that at leastindirectly characterizes the rotational speed of the drive motor and anactual value of the variable that at least indirectly characterizes therotational speed of the drive motor, a change of the rotational speed ofthe drive motor is obtained by

[0007] a) control and/or

[0008] b) regulation of the power consumption, especially the momentconsumption at a specific rotational speed of the hydrodynamic coupling.

[0009] The “variable that at least indirectly characterizes therotational speed of the drive motor” is in the process understood to beeither a variable that is in a proportionality ratio to the rotationalspeed of the drive motor, so that on this variable the rotational speedof the drive motor can be determined, in particular, calculated orderived, or the rotational speed of the drive motor is determineddirectly.

[0010] The solution according to the invention offers the advantage thatin addition to an open controllability of energy-optimized andconsumption-optimized operating points in the performancecharacteristics of the drive motor in the embodiment of the drive motoras an internal combustion engine, a transfer of high moments is readilypossible at low rotational speeds and the power of the drive motor thatis to be provided, that is necessary for this and that can betransmitted, can be kept low.

[0011] In an additional embodiment of the invention, the control and/orregulation of the power consumption of the hydrodynamic coupling is donevia the control and/or regulation of the filling ratio of thehydrodynamic coupling. In this process, a control is desired in thesimplest case. The filling ratio control is done in the processpreferably via the application of an influential pressure onto a staticmedium, in particular, the operating medium level that becomes set in anoperating medium storage device in the context of an operating mediumsupply device. In this process, a portion of the operating mediumlocated in the working space is conducted during the operation of thehydrodynamic coupling in a closed circulation system between at leastone outlet from the toroid-shaped working space between the pump wheeland the turbine wheel and at least one intake into the toroid-shapedworking space, whereby the intake is coupled to a closed operatingmedium storage unit that is closed off from the environment in apressure-tight manner. Upon the appearance of a regulation deviation, acontrolling variable is then created in order to generate an influentialpressure on the static medium in the operating medium storage unit andthe controlling device is regulated. The filling or emptying is thendone until the setting of a pressure scale between the operating mediumlevel in the operating medium storage device and the rotating closedcirculation cycle.

[0012] In an additional embodiment of the invention, additionalfunctions can be realized with the open controllability of individualpoints in the performance characteristics of the drive motor by thecontrol of the filling ratio, if necessary, also taking into accountadditional parameters. Included in this are:

[0013] a) the creation of a complete separation between the motor andoperating machine;

[0014] b) the creation of a rigid connection between the motor andoperating machine;

[0015] c) the function of vibration damping via adjustment of the slip.

[0016] Preferably, the option of the rotational speed regulation isprovided during the entire start-up period in a drive train, i.e. thetime duration of the operation of the hydrodynamic coupling.

[0017] In a further embodiment, the process according to the inventionis a component of the controlled system of a control for the poweroutput of the drive motor. This offers the advantage of simplerealization of an outside control of the power requirement of the drivemotor without direct influence of the drive motor, in particular,without required control of the power output stage, which leads to areduction of the control-technical and regulation-technical expense.

[0018] In an advantageous embodiment based on this further development,this process forms a portion of the control system for the adjustment ofa constant and temporally independent holding moment for the holdingfunction of a machine. By this special control function, theconventional brake devices, for example, in keeping a vehicle on aslope, can be relieved.

[0019] Another possibility consists in integrating the rotational speedregulation of the drive motor in a control for adjustment of a constant,neither time-dependent nor motor rotational speed-dependent outputspeed, i.e. rotational speed on the main drive pinion, for example, of amachine.

[0020] An essential advantage of this process consists, furthermore, inthat in order to create the individual control and regulation functions,only at least the variables named in the following must be taken intoaccount for the control operation:

[0021] the current actual rotational speed of the drive motor;

[0022] the current actual rotational speed on the main drive pinion ofthe hydraulic coupling

[0023] the rotational direction of the main drive pinion;

[0024] a variable characterizing, at least indirectly, a desiredrotational speed of the drive motor that is to be set, and

[0025] optionally, internal state variables for describing thefunctional method of individual components of the drive train.

[0026] The expense for the preparation of corresponding detectiondevices can thus also be kept low and/or is limited to the detectiondevices already existing in the drive train.

[0027] The solution according to the invention for the rotational speedcontrol, in particular, the setting of the rotational speed of the drivemotor as a function of the filling ratio, is not limited to a concreteembodiment of the drive train with hydrodynamic coupling as the starterelement. In this way, the drive motors can be designed in the form ofinternal combustion engines or electro-motors. Usage can be done instationary systems or mobile devices, preferably in the motor vehicle.

[0028] The solution according to the invention is explained in thefollowing using the drawings. The following are shown in detail in them:

[0029]FIGS. 1a and 1 b show in a schematically simplified representationusing block switching diagrams and signal flow diagrams, the fundamentalprinciple of a process according to the invention for regulating therotational speed and the design of the control device;

[0030]FIG. 1c shows, using a signal flow diagram, a process for therotational speed control of the drive motor with integrated control ofthe power that can be consumed by the hydrodynamic coupling;

[0031]FIG. 2 shows, using a schematic diagram of a hydrodynamic couplingand the operating medium supply system allocated to it, the fundamentalprinciple of the filling ratio control;

[0032]FIG. 3 shows, using the rotational speed/torque performancecharacteristics of a drive motor, a comparison of the characteristicline of the hydrodynamic coupling with conventionally operated starterelements;

[0033]FIG. 4 shows, using a signal flow diagram, the possibility ofcontrolling the power output of the drive motor.

[0034]FIG. 1a shows in a schematically simplified diagram using a blockswitching diagram, the fundamental principle of a process according tothe invention for controlling the rotational speed of a drive motor 1 ina drive train 2 during the start-up period. The drive train 2 includesin the process at least one starter element 3 that can be coupled atleast indirectly to the drive motor 1 and that is designed as ahydrodynamic coupling 4, including at least one primary blade wheel 5functioning as a pump wheel and a secondary blade wheel 6 functioning asa turbine wheel, which form with each other at least one toroid-shapedworking space 7. The drive motor 1 is preferably designed as an internalcombustion engine in motor vehicles in the preferred usage of theprocess according to the invention. However, embodiments as electricmotors are also conceivable. The starter element is preferablyintegrated in a gear structural unit 8.

[0035] According to the invention, the rotational speed control of thedrive motor 1 is done as a function of the motor torque M as a functionof the possible consumable torque M_(cons) by the hydrodynamic coupling4. In other words, the level of the power P_(cons) that can be consumedby the hydrodynamic coupling 4, in particular, the level of theconsumable moment, which essentially corresponds to the power P_(transM)that can be transmitted by the drive motor 1, or this power reduced bythe required power for the drive of the additional assemblies orside-assemblies, thus determines the transmittable moment M, based onthe characteristic relation, allocated to a certain filling ratio FG ofthe coupling, between the rotational speed ratio n_(T)/n_(P) thatbecomes set, of the individual blade wheels of the hydrodynamic couplingand the performance number. Via the consumable power, the rotationalspeed of the pump wheel n_(P) is produced and thus the rotational speedn_(M) of the drive motor 1 corresponding to it, or at least proportionalto it.

[0036] The regulation of a certain rotational speed n_(M target) of thedrive motor 1, depending on the power P_(cons) that can be consumed bythe hydrodynamic coupling 4, is done by the control or preferablyregulation of the power consumption of the hydrodynamic coupling 4,according to FIG. 1 a and the signal flow diagram corresponding to FIG.1b, i.e. regulation of the consumable power P_(cons), as shown using asignal flow diagram in FIG. 1c.

[0037] The variable of the consumable power P_(cons) is a function ofthe filling ratio FG of the hydrodynamic coupling 4. Thus, the fillingratio FG is controlled.

[0038] According to the device, the drive motor 1 has assigned to it,for this purpose, a control and regulation device 9, including at leastone control and/or regulation device 10, which has at least onecomparison device 11, in which at least one target value for a variablethat at least indirectly describes the rotational speed n_(M) of thedrive motor, preferably the rotational speed n_(M) target, is comparedwith an actual value of a variable that characterizes the rotationalspeed of the drive motor at least indirectly, preferably the actualrotational speed n_(M) actual. From the regulation deviation Δn_(M)between the target-rotational speed n_(M target) and the actualrotational speed n_(M) actual of the drive motor 1, a correctingvariable is formed for the control of the power P_(cons) that can beconsumed by the hydrodynamic coupling 4, in particular, by the primaryblade wheel 5. For the desired control, shown in FIG. 1c, of the powerP_(cons) that can be consumed, the target variable P_(cons target) isformed from the correcting variable and compared continuously with thecurrent actual variable P_(cons actual). The detection of the actualvalue of the consumable power P_(cons actual) is done in the process inthe simplest case by detection of the variables that at least indirectlydescribe the power, moment m actual, and rotational speed m actual, forwhich purpose, the corresponding detection devices would be provided.The regulation deviation ΔP_(cons) then leads to a corresponding changeof the correcting variable y. For the correcting variable y to takeeffect, a device for changing and/or influencing 12 the powerconsumption is assigned to the hydrodynamic coupling 4. This isintegrated in the control system 13 of the rotational speed control inregard to the active path. The device for changing and/or influencing 12the power consumption includes in the process mechanisms 14 for changingthe filling ratio during the start-up period. In the process, thefilling ratio change is preferably done by filling control through theapplication of an outside pressure onto a static medium in order togenerate a pressure scale between a closed rotating circulation systemand the static medium. The closed rotating circulation system ispressure-impermeable, i.e. the inflow and outflow spaces out of theworking space of the hydrodynamic coupling and the line connectionbetween them are constructed so that they are impermeable to pressuremedium. This pressure, which is also called an influential pressurep_(B), is generated, for example, using a pressure regulation valve 15,which is a component of the mechanism 14 for changing the filling ratio.

[0039] The principle of the application of an outside pressure onto astatic medium is shown in detail in FIG. 2 using a schematic diagram ofa hydrodynamic coupling 4 and the operating agent supply system 18 thatis assigned to it. In the process, a portion of the operating mediumpresent in the hydrodynamic coupling in the toroid-shaped working space5 circulates in a closed circulation system 19. The closed circulationsystem 19 is designed in the process as a cooling medium circulationsystem, i.e. during the operation of the hydrodynamic coupling 4,operating medium is conducted in specific quantities out of the workingspace 7, especially from the outlet 20 out of the working space 7, andvia at least one intake 21 into the working space 7. For this purpose, aconducting system 22 is provided. In this system, mechanisms 23 arearranged for the discharge of heat, for example, in the form of a heatexchanger. The conducting of the operating medium out of the workingspace 7 and into the working space 7 in the closed circulation system 19functions, in the process, mainly for the cooling of the operatingmedium, in particular in order to create a continuous cooling operatingmedium flow. The operating medium supply system 18 contains an operatingmedium storage device 24 that is designed so that it ispressure-impermeable, for example, in the form of a operating medium panin a container or tank, which can be coupled via at least one connectionchannel 25 to the closed circulation system 19 in the area of the intake21. The operating medium storage device 24 is thus arranged in such away that the operating medium level 26 that becomes set is preferablyarranged beneath the toroid-shaped working space 7. Onto the operatingmedium level 25, an influential pressure p_(B) is applied in order tochange the filling ratio FG, whereby in acting on the closed tank, itlets operating medium into the working circulation system in thetoroid-shaped working space via the connection channel 25 until thepressure forms a pressure equilibrium in the area of the intake 21 afterthe heat exchanger.

[0040]FIG. 1b shows, using a signal flow diagram, the interaction of theindividual elements in the overall active path 27 of the rotationalspeed control during the control of the consumable power P_(cons). Thecontrol device 16 corresponds functionally to the control and regulationdevice 10. The control system 13 forms in the process that part of theactive path, which represents the area of the drive train 2 to beinfluenced. Via the control device 16, the influence of the controlsystem 13 is caused via an acuator 17, which is formed from the pressureregulation valve 15. The operating medium storage device 24, designed sothat it is pressure-impermeable, and the hydrodynamic coupling 4,function as additional conduction elements. The power P_(cons) that canbe consumed by the hydrodynamic coupling 4 as a function of the fillingratio FG thus corresponds to a specific moment M_(KP) and a specificrotational speed n_(KP), from which the power P_(trans M) that can betransmitted by the drive motor 1 can be determined and thus, as afunction of the moment assigned to the filling ratio FG, the rotationalspeed n_(M) of the drive motor 1 can be determined.

[0041]FIG. 1c shows, using a signal flow diagram, the interaction of theindividual elements in the overall active path of the rotational speedcontrol 28 during the control of the consumable power P_(cons). Theactive path for the control of the consumable power P_(cons) isindicated here by 29. Moreover, the control system 13 corresponds to theone described in FIG. 1b, and for this reason, the same referenceindicators are used for the same elements.

[0042] The solution according to the invention makes it possible toadjust the rotational speed n_(M) of a drive motor 1 in such a way thatan optimal behavior of the drive motor can be achieved in regard to thestart-up period. In the process, each individual operating point can bestarted up separately or stationarily, i.e. set, in the performancecharacteristics of the drive motor 1. This is done depending on thecontrol or regulation of the power that can be consumed by thehydrodynamic coupling.

[0043] A significant criterion for the rotational speed regulation isformed in the process by the no-load run-up of a drive motor 1, inparticular, the emission-optimized operation in embodiments for use inmotor vehicles, when developed in the form of an internal combustionengine. Since the power consumption of the starter element, inparticular, of the hydrodynamic coupling, is dependent on itself and noton a machine that is connected to it at least indirectly on the maindrive pinion side, it is to be taken into account during theinstallation of an element of this type between the drive motor 1 andthe main drive pinion, that for each load condition, between the drivemotor 1 and the hydrodynamic coupling, there must also be an equilibriumstate with regard to the torque and the rotational speed. The power thatcan be transmitted by the drive motor is, in the rarest case, fullyavailable, during the start-up period, to the gear structural unit(transmission) arranged after the starter element, and thus to thehydrodynamic structural element. The power for auxiliary machines, suchas fans, light machines, pumps, etc., which are arranged prior to thestarter element, must in the process be drawn from the drive output thatis available. During the start-up period at low rotational speeds, it isthus necessary in order to operate the drive motor as much as possiblein the consumption-optimized range, to transmit as large a moment aspossible even at very low rotational speeds. A process of this type canbe obtained by a targeted filling ratio change. The power that can beconsumed via the hydrodynamic coupling causes, in the process, a changeof the rotational speed of the drive motor 1. FIG. 3 shows the possiblestart-up characteristic lines, set opposite each other, of differentstarter elements 4 a-4 c, and a hydraulic-coupling 4 that is controlledor regulated according to the invention during the start-up period withregard to the possible power consumption, in the rotational speed/torqueperformance characteristics of the drive motor 1. The moment line of thedrive motor is indicated by II. The indicators named in the followingare assigned to the individual start-up characteristic lines:

[0044] 1. Trilok-transformer—I_(4a)

[0045] 2. Trilok-transformer with bypass—I_(4b)

[0046] 3. Hydrodynamic coupling with bypass—I_(4c)

[0047] 4. Hydrodynamic coupling controlled according to theinvention—I_(a)

[0048] From the characteristic lines it can be seen that with thesolution according to the invention, a controlled and no-load run-up ofthe drive motor 1 and an operation in the emission-optimized range ofthe drive motor, especially of the internal combustion engine, ispossible. Furthermore, the transmittability of high moments isincreasingly shifted towards low rotational speeds of the drive motor.

[0049] In another embodiment of the invention, the rotational speedregulation of the drive motor is integrated in a control 31 of the poweroutput of the drive motor 1 without direct influence of the main drivepinion. This embodiment indicates a control device 32 for comparison ofa target value for the transmittable power P_(trans M target) to anactual value P_(trans M actual). The transmittable power P_(transM) isdetermined in the process, among other things, by the rotational speedn_(M). The regulation of the rotational speed is done here, with regardto the observational method, in terms of effect in the context of thecontrolled system 33 of the control 31.

[0050] The open controllability of the filling ratio of the hydrodynamiccoupling makes possible, furthermore, for corresponding controlspecification, the setting of a constant, time-independent,load-dependent holding moment for holding functions, for example, whenused in motor vehicles, for keeping a motor vehicle on a slope.

REFERENCE INDICATOR LIST

[0051]1 Drive motor

[0052]2 Drive train

[0053]3 Starter unit

[0054]4 Hydrodynamic coupling

[0055]5 Primary blade wheel

[0056]6 Secondary blade wheel

[0057]7 Toroid-shaped working space

[0058]8 Gear structural unit (transmission)

[0059]9 Control and Regulation device

[0060]10 Control and Regulation device

[0061]11 Comparison device

[0062]12 Device for changing and influencing the consumable power

[0063]13 Control system

[0064]14 Mechanism for filling ratio change

[0065]15 Pressure regulation valve

[0066]16 Control device

[0067]17 Actuator

[0068]18 Operating medium supply system

[0069]19 Closed circulation system

[0070]20 Outlet

[0071]21 Intake

[0072]22 Conduit system

[0073]23 Mechanism for discharge of heat

[0074]24 Operating medium storage tank

[0075]25 Connection channel

[0076]26 Operating medium level

[0077]27 Total active path

[0078]28 Total active path

[0079]29 Active path

[0080]30 Control

[0081]31 Control of the power that can be transmitted by the drive motor

[0082]32 Control device

[0083]33 Controlled system

[0084] n_(Mtarget) Target rotational speed

[0085] n_(Mactual) Actual rotational speed

[0086] P_(cons) Consumable power

[0087] P_(cons actual) Actual value of the consumable power

[0088] P_(cons target) Target value of the consumable power

[0089] ΔP_(cons) Power deviation

[0090] P_(trans actual) Actual value of the transmittable power of thedrive motor

[0091] P_(trans target) Target value of the transmittable power of thedrive motor

[0092] P_(B) Influential pressure

[0093] Y Correcting variable

1. Process for rotational speed control of a drive motor (1) during astart-up period in a drive train (2), containing at least one starterelement (3) connected to the drive motor (1) so that it is rotationallyfixed, in the form of a hydrodynamic coupling (4) containing a primaryblade wheel (5) and a secondary blade wheel (6), which together form atleast one toroid-shaped working space (7), characterized in that therotational speed of the drive motor (1) is set as a function of thepower that can be consumed by the hydrodynamic coupling (4), especiallythe consumable moment at a specific rotational speed.
 2. Processaccording to claim 1, characterized in that upon the appearance of aregulation deviation between a variable that at least indirectlycharacterizes the rotational speed of the drive motor and an actualvalue of the variable that at least indirectly characterizes therotational speed of the drive motor, a change of the rotational speed ofthe drive motor (1) is made by the control and/or regulation of thepower consumption of the hydrodynamic coupling (4).
 3. Process accordingto claim 2, characterized in that the control and/or regulation of thepower consumption of the hydrodynamic coupling (4) is obtained using acontrol and/or regulation of the filling ratio of the hydrodynamiccoupling (4).
 4. Process according to claim 3, characterized by thefollowing characteristics: 4.1 a portion of the operating medium isconducted, during the operation of the hydrodynamic coupling (4), in aclosed circulation system between an outlet from the toroid-shapedworking space (7) between the pump wheel (5) and the turbine wheel (6)and an intake into the toroid-shaped working space (7); 4.2 the intakeis coupled to a closed operating medium storage unit that is closed offfrom the environment in a pressure-tight manner; 4.3 that upon theappearance of a regulation deviation, a correcting variable is createdin order to generate an influential pressure on the static medium in theoperating medium storage unit and the adjustment device is regulated. 5.Process according to claim 4, characterized in that the influentialpressure is made via a toothed wheel pump driven by a drive motor (1).6. Process according to claim 1 to 5, characterized in that therotational speed control is performed in a drive train at least duringthe entire start-up period.
 7. Process according to one of the claims 1to 6, characterized in that this part of the controlled system of acontrol is for the power output of the drive motor (1).
 8. Processaccording to one of the claims 1 to 6, characterized in that this partof the controlled system is for the adjustment of a constant andtime-independent holding moment for the stopping function of a drivemotor.
 9. Process according to one of the claims 1 to 8, characterizedin that this part of the controlled system of a control is used to set aconstant main drive pinion rotational speed that is dependent on neithertime nor motor rotational speed.
 10. Process according to one of theclaims 1 to 9, characterized in that at least the variables named in thefollowing are taken into consideration for the control process: thecurrent actual rotational speed of the drive motor; the current actualrotational speed on the main drive pinion of the hydraulic-coupling; therotational direction of the main drive pinion; a variable that at leastindirectly characterizes a desired rotational speed of the drive motorthat is to be set and optionally, internal state variables fordescribing the functional method of individual components of the drivetrain.
 11. Process according to one of the claims 4 to 10, characterizedin that the correcting variable is parameter-dependent.
 12. Use of aprocess according to one of the claims 1 to 11, in a drive train (2)with a drive motor (1) in the form of an internal combustion engine. 13.Use of a process according to one of the claims 1 to 11, in a drivetrain (2) with a drive motor (1) in the form of an electromotor.
 14. Useof a process according to one of the claims 12 or 13 in a motor vehicle.15. Use of a process according to claim 12 or 13 in a stationary system.16. Control and/or regulating device (9) for performing the processaccording to one of the claims 1 to 11, characterized by the followingcharacteristics: 16.1 by a control and/or regulating device (10); atleast one comparison device (11) for comparing a target value of avariable that at least indirectly describes the rotational speed of thedrive motor to an actual value; 16.2 the control and/or regulatingdevice (10) is connected to a device for detecting the actual value of avariable that at least indirectly describes the rotational speed of thedrive motor and a device for the specification of a target value for therotational speed of the drive motor; 16.3 the control and/or regulatingdevice (10) contains at least one comparison device (11) for comparing atarget value of a variable that at least indirectly describes therotational speed of the drive motor to an actual value; and a device forforming a target value for the filling ratio of the hydrodynamiccoupling; 16.4 the control and/or regulating device (10) contains atleast one beginning element, which is coupled to an actuator in order toinfluence the filling ratio of the hydrodynamic coupling.